1. Field of the Invention
The present invention relates to pipeline valve apparatus and, more particularly, to improvements in valve transmission apparatus.
2. Description of the Invention Background
Various methods and devices for imparting rotary motion to rotary actuated devices are known in industry. For example, ball and butterfly valves that are used for controlling the flow of liquid materials ranging from milk to oil are commonly controlled by rotary actuators that convert linear motion to rotary motion. In addition, rotary actuators have also been used to impart rotary motion to indexing tables on small part assembly lines in the electronics industry. In general, rotary actuators have also been used in a plethora of other process and assembly operations requiring rotary motion. Such rotary actuators, in some applications, are directly linked to the valves or other devices to be rotated. However, it is desirable to have a transmission between the actuator and the valve which alters the speed of rotation and torque between the output shaft of an actuator and input shaft to the valve or other devices. In some applications, the device to be rotated requires greater power than the actuator is capable of producing. In other applications, it is necessary to increase or decrease the speed of rotation of the valve from the speed of rotation of the actuator shaft. Transmissions are desirable which will achieve the increased or decreased torque or speed while transmitting the motion from the actuator to the valve.
Heretofore, valve transmissions have been of various types including, for example, a transmission which has an actuator and transmission integral with one another. This transmission has a piston, which when actuated, drives a rack in lateral alignment with the piston to turn a pinion. Such an arrangement severely limits the versatility of the transmission as the actuator and transmission are one unit. Also, in order to change the gear ratio or other operating characteristics of such a transmission, the entire actuator/transmission unit must be replaced. A transmission is needed which provides for a simple method of changing the gear ratio without replacing the entire actuator.
A transmission is also needed which includes electronic and mechanical monitoring systems to indicate the position of the valve.
A transmission is further needed which will permit accurate, efficient and effective conversion of the linear motion of an actuator to rotary motion for an object to be rotated.
The present invention is directed toward an improved design for a valve transmission apparatus which overcomes, among others, the above discussed problems.